import math

x1,y1,x2,y2=map(float,input().split())

a = ((x1-x2)**2)+((y1-y2)**2)

a = math.sqrt(a)

print('{:.8f}'.format(a)) import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 a = ((x1-x2)**2)+((y1-y2)**2) a ((x1-x2)**2)+((y1-y2)**2) (x1-x2)**2 x1-x2 x1 x2 2 (y1-y2)**2 y1-y2 y1 y2 2 a = math.sqrt(a) a math.sqrt(a) math.sqrt math sqrt a print('{:.8f}'.format(a)) print '{:.8f}'.format(a) '{:.8f}'.format '{:.8f}' format a x2,y2=map(float,input().split()) map(float,input().split()) x2 y2=map(float,input().split()) map(float,input().split()) y2 a = ((x1-x2)**2)+((y1-y2)**2) ((x1-x2)**2)+((y1-y2)**2) a y1,x2,y2=map(float,input().split()) map(float,input().split()) y1 x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 a = math.sqrt(a) math.sqrt(a) a
import math

x1,y1,x2,y2=map(float,input().split())

a = ((x1-x2)**2)+((y1-y2)**2)

a = math.sqrt(a)

print('{:.8f}'.format(a))
